Rubberlike materials



Patented June 30, 1942 1 UNITED STATES PATENT OFFICE RUBBERLIKE MATERIALS Reginald George Robert Bacon, Bernard James Habgood, and Rowland Hill, Blackley, Manchester, England, assignors to Imperial Chemical Industries Limited Britain a corporation of Great No Drawing. Application February '28, "1940, $35M No. 321,351. In Great'Brltaln March a,

17 Claims. This invention relates to the manufacture of rubber-like materials .of improved oil and solvent-resistance from synthetic rubber-like materials.

By synthetic rubber-like materials are meant the products having rubber-like properties, which are obtained by the polymerisation of butadiene- 1:3 or substitution products of butadiene-lzli,

such as 2-chloro-butadiene-1:3 and methyland.

dimethyl-but adienes-l' m, either alone or in conjunction with lesser quantities of other unsaturated substances which will interpolymerise with them. Examples of these synthetic rubber-like materials are the products which are sold under the name Neoprene.

According to the invention the new rubberlike materials are obtained by treating synthetic rubber-like materials with a minor proportion of dithiocyanoge'n so that interaction takes place.

The new rubber-like materials are distinment is'obtained with higher saturation, in general too much diminutionin rubber-like properties takes place with more than about 30-40% I saturation.

are used they may be brought into interaction with the synthetic rubber-like materials at any convenient stage, for instance before the treatguished from the old by having improved resistance' to oils and. solvents, especially improved resistance to hydrocarbon solvents such as benzene. Many of the synthetic rubber-like materials have much higher resistance to oils and solvents than rubber and this enables them to be used for many purposes for which rubber is unsuitable. By means of the present invention the syntheticrubber-like materials which have high resistance to oils and solvents are converted. to products which have even higher resistance, while those having only moderate resistance,

which are mostly the ones which are most readily and inexpensively synthesised, are converted to oneswith higher resistance.

By minor proportions of dithiocyanogen are meant proportions such that there becomes chemically. combined with the synthetic rubberlike material not more than will yield a product which still possesses rubber-like properties, and

in any case not more-than about 40% of that which would be chemically combined it there werecomplete saturation, that is to say if all the free ethylenic linkages became saturated.

The quantity of dithlocyanogen to be used depends to some extent upon the particular synthetic rubber-like material which is treated. However, in general a noticeable improvement in oil and solvent resistance is obtained when the synthetic rubber-like material is heated with dithiocyanogen in quantity such that there be? comes chemically combined enough to give about 5% saturation. With 15-20% saturation a great improvement in oil and solvent-resistance 'is usument with the dithiocyanogen.

The rubber-like products obtained by the treatment with the dithiocyanogen are in general tough resilient products having the improved oil and solvent-resistance referred to above. The uncured products are suitable for use as oil-resistant pigment bearing diluents for synthetic rubber-like materials.

Vulcanisation can in generalbe effected by the addition of the vulcanising agents used in curing the synthetic rubber-like materials themselves and then heating. Softeners, plasticisers and peptisers may be used along with the rubberlike materials, as also may be reinforcing ingredlents and fillers. The products of the'invention may be used alone or in admixture with rubber or synthetic rubber-like materials.

Theflinvention accordingly includes a process for the manufacture of rubber-like materials which comprises treating synthetic rubber-like materials, which are obtained by the polymerisation ofbutadiene-l:3 or substitution products of butadiene-l:3, such as 2-chlorobutadiene-lz3 and. methyland dimethyLbutadienes, either alone or in conjunction with lesser quantities of other unsaturated substances which will polymerise with them, with dithiocyanogen in quantity suitable to yield a rubber-like material and so that the amount which becomes chemically combined with the synthetic rubber-like material, ,is not in excess of 40% of that which would be combined if there were complete saturation.

The invention also includes the process of vulcanising the rubber-like materials obtained by the aforesaid process, and also the products of the two processes.

ally obtained, and while still further improvc- T et t ent w the dithiocyanogen i rried out conveniently in a liquid which dissolves the rubber-like material or at least causes it to swell, and the dithiocyanogen is conveniently brought into reaction in the form of a solution in the same .liquid or in another liquid such that the two solutions are readily miscible.

Since polymerisation takes place readily in dithiocyanogen solutions, the solutions should be used preferably when freshly prepared. If they are not freshly prepared they should have been kept under conditions where little or no polymerisation takes place, e. g. cold, in the dark, and with the dithiocyanogen at low concentration in the solution.

In a convenient way of carrying the invention into practical effect the synthetic rubber-like material is dissolved in a suitable solvent and stirred, while the dithiocyanogen, which is also in solution, is stirred in so as to obtain a homogeneous mixture. Reaction takes place readily, usually without heating, 1. e. at -25 C. in an internal mixer. Reaction may be regarded as substantially complete when there is no further marked change in the physical characteristics of the mix (e. g. its viscosity). When reaction is complete the solvent is removed, for instance by drying in a vacuum oven or by treating with steam.

Inexpensive easily-recoverable organic solvents, which do not interact with dithiocyanogen or the synthetic rubber-like starting materials under the conditions used, e. g. benzene and carbon tetrachloride, should be used. In cases where the starting rubber-like material areknown to be rendered more plastic by the addition of peptising agents such as thio-p-naphthol, a. treatment with one of these agents may be conveniently given as a preliminary.

The following examples, in which parts are by weight, illustrate but do not limit the invention.

Example 1 A solution of 100 parts of Neoprene (polymerised 2-chlorobutadiene-1:3) in 800 parts of benzene is mixed at about 15 C. with a solution of parts of freshly prepared dithiocyanogen in 380 parts of benzene. After 1 hour, by which time the mixture has set to a limp orange-brown gel, the solvent is conveniently removed in a vacuum drying oven. The residual product, which is a tough rubbery mass, is milled into sheets on a roller mill. 119 parts of product in sheet form are obtained. This milled product is orange! brown in colour, very tough, but elastic, and is found on analysis to contain 3.75% of nitrogen, corresponding to the addition of 0.14 molecule of dithiocyanogen per molecular unit of 2-chloro- Zinc oxide 10 The mix was vulcanised at 141 C. for 1 hour.

The vulcanisate was slightly harder than that obtained with untreated Neoprene, but had a superior resistance to Diesel oil, swelling only 28% compared with 55% in the case of an untreated control. The vulcanisate also had a superior resistance to benzene.

Example 3 A solution of parts of synthetic rubber-like material, made by the polymerisation of butadiene in the Presence of sodium, in 800 parts of benzene, is mixed at about 15 C. with 400 parts of a benzene solution containing 33 parts of freshly prepared dithiocyanogen. Reaction occurs within a hour, leading to the formation of a limp orange-coloured gel which becomes stiffer after keeping for a few hours. The product is allowed to stand overnight and is then dried and sheeted as described in Example 1. An extremely tough but elastic product is obtained which is found on analysis to contain 6.55% of nitrogen, corresponding with the addition of 0.17 molecule of dithiocyanogen per molecular unit of butadiene.

The mix was vulcanised by heating for 1 hour at 141 C. A somewhat hard rubbery product was formed. This product when compared with a vulcanisate made under similar conditions from the same polymerised butadiene, which has not been treated with dithiocyanogen, by immersion in pure benzene, showed less than 50% of the swelling of the untreated control. Similarly when compared by immersion in Diesel oil at 70 C. the product swelled to the extent of 57% of its own volume, as compared with 300%.

Example 5 r 100 parts of synthetic rubber-like material made by interpolymerising butadiene with styrene in the proportion of 7 parts of the former to 3* of the latter are brought into solution by working in a dough mixer with 1000 parts of benzene and 25 parts of dibutyl thiodiglycollate. The solution is stirred at 20 C. with 300 parts of a benzene solution containing 22.2 parts of dithiocyanogen, so that a homogeneous mixture results. Gel formation begins within an hour and is allowed to proceed for 20 hours. The benzene is then removed from the product by heating it at 60 C. in a vacuum oven. There remains a tough but elastic rubber material.

Example 6 The following mixing was made up:

' Parts Product of Example 5 100 Magnesium oxide 10 Stearic acid 2 Pine tar 4 Channel black 40 Sulphur 3 Mercaptobenzthiazole--. 0.75

methylbutadiene-1,3, and polymers of 2,3-di- After curing for 30 minutes at ,141 C. the vulmethylbutadiene-1,3 with from about per cent canisate had the following physical properties to about 40 per cent or the amount of dithiocy- Tensfle strensthflfl; z 1 I filoglglgirnecessary to completely saturate the said giggg gg z g ".T' cent 5 a 5. Process for the manufacture of rubber-like shore elasticity "7 55 materials. having higher resista ce to oils and l Increase in volume upon 168 hours immergeactmg a poslymelf i'g a g g fi 'sion in .Diesel oil at 70 C. per cent of mm about per can a u per Fe the amount of dithiocyanosen necessary to cominitlal volume 64 1 t l t be m s m mer Increase in volume upon 48 hours 'immerp a g t f bb r rke sion in benzene at C. per cent of 1111- rocess 5 man 0 e 1 tial vnmm v 147 materials, having higher resistance to oils and solvents than natural rubber, which comprises A sample of the unmodified interpolymer of bu-' l5 reacting a polymer of 2-chlorobutadiene-l,3 with tadiene and styrene was compounded to the same from about 15 per cent to about per cent of formulmvulcanised and tested, when the followthe amount of dithiocyanogen necessary t ing resultswere obtained: pletely saturate the said polymer.

" l 7. Process for the manufacture of, rubber-ilk Tensile strength 150 20 materials, having higher resistance to oils and Elongation at break "per cent-.. 285 Shore hardness 72 solvents than natural rubber, which comprises shore elasticity 60 dissolving a polymer of 2-chlor0butadiene-l,3 in

a a solvent therefor, dissolving dithiocyanogen in a Resilience per cent 57.7 Increase in volume upon 168 hours immeb solvent therefor which is miscible with the polysion in Diesel on at C" per cent ofiimt mersolvent, and reacting the said polymer with u a] vnmmp I 154 from about-5 per cent to about per cent of the Increase in volume upon '48 hours immeramqunt of ditmocyanogen necessary,t Complete sion m benzene at C" per cent of ly saturate the. said polymer by mixing the reti a1 volnmp 298 actants in solution.

' 4 3o 8. Process for the, manufacture of rubber-like Resilience was re on an instrument as materials, having higher resistance to oils and scribed b nett 8: Matthews, Ind. 8r Eng-Chem. solvents than natural rubber, which comprises 1934, 26, 1292, and is expressed as a percentage wm a polymer of zmdi qg i energy return. a solvent therefor, dissolving dithiocyanogen in a We claim: 35 solvent therefor which is miscible with the poly l '1. Process for the manufacture of rubber-like m t, and reacting the said polymer with materials, having=higher resistance to oils and fr m t'm r t t b t 20 per t of so e ts than natural u which c ses the amount of dithiocyanogen necessary to comre ctii'i a P ym ri ma eri l, of the group conpletely' saturate the said polymer by mixing the sisting of polymersof butadiene-L3, polymers of W reactants i l t a-chiorobutadiene-lfi, oly s of 2methy1buta- 9. Process of claim 8 further characterized in (hone-1,3, polymers of 2,3-dimethy'lb t di that the rubber-like material'is compounded and and interpolymers of said dienes with lesser quanulcanized titles of other unsaturated substances which will 10, A rubber-like material comprising a synpo e e t h with from aboutfi per ce thetic rubber-like polymeric material, of the to about40 per cent of the amount of dithiocyangroup consisting of polymers of butadiene1,3, ogen necessary to saturate completely said poly-- polymers of 2 -chlorobutadiene-1,3, polymers of 2- meric material. methylbutadiene-l,3, polymers of 2,3-dimethyl- 2 Process for the manufacture of rubber-like butadiene-L3, and interpolymers of said dienes materials, h vi higher resistance to Oils and with lesser quantities of other unsaturated subsolvents than natural rubber, which comprise stances which will polymerize with them, having, dissolving a i ymericmaterial, of the group 00 1- in chemical combination therewith, from about 5 ti of p ymers of butadicne po y s o per cent to about 40 per cent of the amount of -chlo o ut c -L po f y dithiocyanogen necessary to saturate completely tadiene-L3, polymers of 2,3-dimethylbut ien said polymeric material.

', 1,3, and interpolymers of said clienes with lesser 11. A vulcanized rubber-like material comprisquantities of other unsaturated substances which ing a synthetic rubber-like polymeric material, of will polymerize with them, in a solvent therefor, the group consisting of polymers of butadiene-1,3, dissolving dithiocyanogen in a solvent therefor, polymers of 2- chlorobutadiene-L3, polymers of 2- which is miscible with the solvent for the polymethylbutadiene-LB, polymers of 2,3-dimethylmeric material, and reacting said polymeric mabutadiene-1,3, and interpolymers of said dienes terial with from about 5 per cent to about 40 per with lesser quantities of other unsaturated subcent of the amount of dithiocyanogen necessary stances which will polymerize with them, having, to saturate completely said polymeric material in chemical combination therewith, from about 5 by mixing the reactants in solution. per cent to about 40 per cent of the amount of 3. Process of] claim 2 further characterized in dithiocyanogen necessary to saturate completely that the rubber-like material is compounded and said polymeric material.

' vulcanized. l 12. A rubber-like material comprising a syn- 4. Process for the manufacture of rubber-like thetic rubber-like polymeric material, ,of the materials, having higher resistance to oils and group consistlng of polymers of butadiene-1,3,

1 solvents than natural rubber, which comprises polymers of 2-chl0robutadiene-1,3, polymers of 2- .reactinga synthetic rubber-like diene polymer of v methylbutadiene-1,3, polymers of 2,3-dimethylthe group consisting of polymers of butadiene- 1,3, butadiene-LB, and interpolymers of said dienes polymers of 2-chlorobutadiene-l,3, polymers of 2- with lesser quantities or other unsaturated substances which will polymerize with them, having, in chemical combination therewith, from about 15 per cent to about 20 per cent of the amount of dithiocyanogen necessary to saturate completely said polymeric material.

13. A vulcanized rubber-like material comprising a synthetic rubber-like polymeric material. of the group consistingof polymers of butadiene- 1,3, polymers of 2-cli1orobutadiene-L3, polymers of 2-methylbutadiene-l,3, polymers of 2,3-dimethylbutadiene-1,3, and interpolymers of said 15. A rubber-like material comprising a polymer o1 2-chlorobutadiene-1,3 having, in chemical combination therewith, from about 15 per cent to about 20 per cent or the amount of dithiocyanogen necessary to completely saturate the said polymer.

16. A vulcanized rubber-like material comprising a polymer of 2-chlorobutadiene-L3, having. in chemical combination therewith, from about 5 per cent to about 40 per cent of the amount of dithiocyanogen necessary to completely saturate the said polymer.

17. A vulcanized rubber-like material comprising a polymer or 2-chlorobutadiene-1,3 having, in chemical combination therewith, trom about 15 per cent to about 20 per cent of the amount of dithiocyanogen necessary to completely saturate the said polymer.

REGINALD GEORGE ROBERT BACON, BERNARD JAMES HABGOOD. ROWLAND HILL. 

